Optical recording medium

Abstract

A tape-shaped optical recording medium, in which a recording layer capable of optically recording or reproducing information signals is formed on a flexible base, is disclosed. A protective film formed of a soluble high polymer having a contact angle with respect to water of not less than 100° C. and a glass transition temperature of not lower than 100° C. is formed on the recording layer. The soluble high polymer may be a fluorine-based polymer, such as a tetrafluoroethylene-dioxole copolymer. The protective film has a film thickness in a range of from 0.25 λ/n to 0.5 λ/n, where λ is a wavelength of a playback light and n is a refractive index of the protective film.

What is claimed is: 
     
       1. An optical recording medium comprising a flexible base and a recording layer adapted for recording and/or reproducing the information formed thereon, said recording layer having formed thereon a protective film of a high polymer material having a contact angle with respect to water of not less than 100° with respect to water at 25° C. and a glass transition temperature of not lower than 100° C.,   said protective film having a film thickness of not less than 0.25 λ/n and not more than 0.5 λ/n, where λ is a wavelength of a playback light and n is a refractive index of the protective film.   
     
     
       2. An optical recording medium as claimed in claim 1 wherein the refractive index n is in the range of from 1.25 to 1.5. 
     
     
       3. An optical recording medium as claimed in claim 1 wherein the high polymer is a fluorine-based polymer. 
     
     
       4. An optical recording medium as claimed in claim 1 wherein the high polymer is a tetrafluoroethylene-dioxole copolymer. 
     
     
       5. An optical recording medium as claimed in claim 1 wherein the optical recording material contained in the recording layer is an organic optical recording material.